Porous materials, which have a large surface area, have been used widely as a catalyst support and a support for the dispersion and retention of an enzyme, a functional organic compound, or the like. Above all, a porous material having a sharp pore size distribution of pores forming a porous structure has a molecular sieve function, and thus can be applied to a material separation agent and the like. In recent years, as a porous material having uniform and fine pores, mesoporous silica having pores with a meso-scale diameter has been developed and attracting attention as a material to be applied to a controlled release material, an electronic material, an optical material, and the like as well as a material separation agent, a catalyst support, and the like.
Mesoporous silica can have various morphologies, such as a spherical shape, a fiber shape, a film shape, and a particle shape that includes a silica-containing outer shell portion with a mesoporous structure and a hollow portion present on an inner side relative to the outer shell portion (hollow mesoporous silica particles).
Patent Document 1 discloses a method for producing hollow mesoporous silica particles having an average primary particle size of 0.05 to 10 μm and an average pore size of 1 to 10 nm. According to this production method, a mixed solution containing a surfactant, a hydrophobic organic compound, and a silica source that yields a silanol compound by hydrolysis is stirred, resulting in oil droplets containing the hydrophobic organic compound with a silica-containing mesoporous layer formed around the oil droplets. Then, the oil droplets are removed from composite silica particles that contain the mesoporous layer and the oil droplets embedded inside the mesoporous layer, thereby obtaining hollow mesoporous silica particles.